Tool, tool system and method for the production of particle foam parts

ABSTRACT

A tool for the production of particle foam parts through the welding of foam particles by means of electromagnetic waves comprises two mould halves which bound a mould cavity. At least one of the two mould halves is made of a material which is transparent to electromagnetic waves and has a boundary wall which bounds the mould cavity and one or more supports serving to support the boundary wall on a capacitor plate on the side facing away from the mould cavity and forming one or more hollow spaces. A tool system for the production of particle foam parts has the tool and at least one trimming body, which is designed for introduction into the hollow space or at least one of the hollow spaces. A method for the production of a particle foam part with the tool or tool system is also specified.

RELATED APPLICATIONS

This application is a § 371 National Phase Application of InternationalApplication No. PCT/EP2020/077858, filed on Oct. 5, 2020, nowInternational Publication No. WO 2021/073924 A1, published on Apr. 22,2021, which International Application claims priority to GermanApplication 10 2019 127 680.2, filed on Oct. 15, 2019, both of which areincorporated herein by reference in their entirety.

The present invention relates to a tool, a tool system and a method forthe production of particle foam parts.

The tool and the tool system for the production of particle foam partsmake use of electromagnetic waves, wherein foam particles are weldedinto a particle foam part by means of the electromagnetic waves. Theenergy required for welding is applied to the foam particles by means ofthe electromagnetic waves.

For a long time now, attempts have been made to weld foam particles intoparticle foam parts by means of electromagnetic waves. Relevant methodsare disclosed for example by U.S. Pat. Nos. 3,079,723, 3,242,238 and GB1,403,326.

Described in U.S. Pat. No. 3,079,723 is a method for the sintering ofmoist thermoplastic foam particles. The particles are heateddielectrically and simultaneously compacted in the mould.Electromagnetic waves with a frequency of around 2 to 1000 MHz areapplied.

A similar method is disclosed by U.S. Pat. No. 3,242,238, in which foamparticles are wetted with an aqueous solution and subjected to anelectromagnetic field with a frequency of around 5 to 100 MHz.

Described in GB 1,403,326 is a method for the welding of expandablepolystyrene foam particles, in which the particles are wetted with anaqueous solution and subjected to an electromagnetic field of 5 to 2000MHz.

Considerable efforts have also been made in recent decades to weld foamparticles using electromagnetic waves. Relevant methods are described inWO 01/064414 A1 and WO 2013/050581 A1.

WO 01/064414 A1 discloses a method in which polymer particles ofpolyolefins, which are wetted by a liquid medium, are heated byelectromagnetic waves, in particular microwaves. Here the temperature inthe mould is regulated by control of its internal pressure.

Described in WO 2013/050581 A1 is a method for the production ofparticle foam parts in which a mixture of foam particles and dielectrictransfer fluid is heated by means of electromagnetic waves, in order tofuse the foam particles into a particle foam part. Radio waves ormicrowaves are used as electromagnetic waves. The material of the foamparticles is made of polypropylene (PP).

Despite these long, sustained and considerable efforts, there are nomachines on the market for the welding of foam particles usingelectromagnetic waves. Only machines for welding foam particles usingsteam are in commercial use.

There are no machines for the welding of foam particles at the seriesproduction stage, even though the associated benefits have long beenknown. These are in particular:

-   -   more efficient energy input    -   after welding, the foam particles are dry, and may immediately        be used in further processing    -   heating is from the inside to the outside, so that the inner        zone of the foam particles may be significantly better welded,        and    -   equipment for the generation of steam, which is much more        expensive than a generator of electromagnetic waves, may be        dispensed with.

The applicant for the present patent application has developed apparatusfor the welding of foam particles using electromagnetic waves, and thecorresponding method, to the point where it is in a position to producefairly large quantities of foam particles by means of prototypes closeto series production standard, through welding of foam particles bymeans of electromagnetic waves. These apparatus variants and methods arebased on the technology described in WO 2017/127310 A1, WO 2017/127312A1 and WO 2018/100713 A2, to which reference is made to the full extentin terms of their disclosed content, also in connection with theinvention described below and in particular, additionally but notexclusively, relating to the apparatus variants and methods plusmaterials.

Herewith there has been success in obtaining uniform welding in particlefoam parts using different moulds. The more complex the mould of theparticle foam part, the more difficult it is to achieve uniform weldingof the foam particles. For decades it has been known that such foamparticles in a plastic cup with some water may be placed in aconventional domestic microwave oven, and a good even welding may beachieved. If however the particle foam parts to be produced are largeror more complex in form or strongly contoured or of irregular thickness(measured in a direction perpendicular to the capacitor plates, i.e. inthe direction of propagation of the electromagnetic field), then it isdifficult to obtain a uniform distribution of the electromagnetic fieldin all places. The problems have a wide variety of causes. On the onehand, electromagnetic waves do not in principle have the same energydensity throughout. The shorter the wavelength, the greater the localfluctuations. On the other hand, electromagnetic waves are influenced bythe material of the tool bounding the mould cavity. Here there arevarious effects. On the one hand, some of the energy of theelectromagnetic waves may be absorbed by the material of the mouldingtool. On the other hand, this material functions as a dielectric whichis polarised in such a way that an electromagnetic field opposite to theelectromagnetic waves is generated. Through this, the energy density ofthe electromagnetic waves is shifted and may be concentrated locally inthe mould cavity. The inventor of the present invention has taken thisinto account for the first time in development of the present invention.

Furthermore, the material of which the foam particles are made may havean effect on the electromagnetic field, so that, with use of differentmaterials, the same tool acts in a different way.

In the RF foaming of complex geometries it is therefore desirable forthe electrical field to be as constant or uniform as possible in allareas of the moulding. There are suggestions for achieving this forexample by deformation of electrodes and variation of tool wallthickness. However, this is linked to the application of very complexsimulation programs. The problem here is that the relative permittivityof tool material and particle foam vary greatly, for example by a factorof 2 to 5.

A further problem lies in the fact that it is practically impossible tooptimise the tools for RF foaming retrospectively, if for example theelectrical field needs to be strengthened in some areas.

Since heating with an RF field proceeds from the inside to the outside,welding of outer particle layers is poorer than in the core, and thesurface may remain rough. In order to improve this, heating and coolingchannels have formerly been provided in the tool.

For technical process reasons it may be sensible for the foam particlesto be fed into the mould cavity mixed with water as heat transfermedium. During welding, the water may then be pressed out of the mouldcavity. By this means, the average relative permittivity in the mouldcavity may vary and with it also the local electrical field strength.Control of such a process is difficult.

In an apparatus for the production of particle foam parts, the aim is toproduce different particle foam parts. For this purpose one must changeover the relevant tools which define a mould cavity in which theparticle foam parts are moulded. This is already well-known fromconventional apparatus for the production of particle foam parts, inwhich the foam particles are welded using steam. The inventors of thepresent invention have however recognised that, other than in thewelding of foam particles by means of steam, in welding by means ofelectromagnetic waves the function of a tool depends on the shape, whichis preset by the shape of the particle foam part to be produced. This isone of the main reasons why, despite the most intensive experiments anddevelopment efforts over decades, there has been no success indeveloping apparatus suitable for series production for the welding ofparticle foam parts by means of electromagnetic waves, in particularparts with an irregular shape or thickness or strong contouring.

The invention is therefore based on the problem of creating a tool forthe production of particle foam parts, together with a correspondingtool system, by which foam particles may be welded by means ofelectromagnetic waves, reliably and with high quality, in a simplemanner.

A problem of the present invention is in particular to specify a tool, atool system and a method which avoid the above-mentioned disadvantagesand problems, or at least improve them.

A further problem of the present invention is to provide scope forretrospective optimisation of such a tool.

A further problem of the present invention is to improve a tool, a toolsystem and a method in respect of uniform quality of welding in thecross-section of the particle foam part.

A further problem of the present invention is to provide scope forbalancing out any change in relative permittivity in the mould cavityduring the foaming process, and/or to influence during the foamingprocess the electromagnetic field prevailing in the mould cavity, inparticular in respect of electrical field strength.

One or more of the stated problems is or are solved by the subjects ofthe independent patent claims. Advantageous developments are set out inthe respective dependent claims.

The tool according to the invention for the production of particle foamparts through the welding of foam particles by means of electromagneticwaves includes two mould halves which bound a mould cavity. At least oneof the two mould halves is made of a material which is transparent toelectromagnetic waves and has a boundary wall which bounds the mouldcavity and one or more supports serving to support the boundary wall ona capacitor plate on the side facing away from the mould cavity andforming one or more hollow spaces of the mould half.

Due to the forming of hollow spaces on the side of the boundary wallfacing away from the mould cavity, mould halves of any desired shape maybe realised with a minimum of material. The influencing of theelectromagnetic field in the mould cavity by the material of the mouldhalf may therefore be limited. Surprisingly, simulations such as testshave revealed that the supports cause hardly any discontinuity or lackof homogeneity of field strength in the mould cavity. Instead, the fieldstrength between areas corresponding to the supports and areascorresponding to the hollow spaces averages out and this averaging outor evenness continues into the mould cavity. In other words, there is anaveraging of the permittivity levels of the material of the mould halvesand the air contained in the hollow spaces which is surprisinglyhomogenous, even if the material of the mould halves s not distributedhomogenously in the hollow spaces located therein. The mould halves aretherefore preferably so designed that they have an average permittivitycorresponding roughly to the permittivity of the foam particles to bewelded. This gives rise to a very homogenous electrical field, even ifthe mould cavity has a complex contour.

It is therefore possible in a simple manner to produce mould halves withsimilar dielectric properties to the object to be produced. Inparticular, harmonisation of the dielectric properties of the mould halfto the particle foam part is possible in a surprisingly simple manner.When the dielectric properties of the mould half correspond roughly tothose of the particle foam part, this also has the advantage that theelectromagnetic field in the whole area between the capacitor plates isroughly homogenous, irrespective of the shape of the mould half or ofthe particle foam part.

Support of the capacitor plate by the supports may be effected directlyor indirectly (i.e. with an intermediate layer). The supports may berealised by side walls and/or intermediate walls. The boundary wall andthe supports may be made in one piece, in particular being monolithic.In the case of some moulds, a capacitor plate already forms a boundaryof the mould cavity. Naturally it is also possible for each of the twomould halves to be made of material which is transparent toelectromagnetic waves, and to have the boundary wall and the support(s).

Preferably the boundary wall of at least one mould half is made withsubstantially constant thickness.

The supports of at least one mould half run preferably parallel to apress direction, by which the mould halves are pressed together by apress during operation.

The mould halves may have connections for a tempering medium, which isable to flow through the one or several hollow space(s).

At least one of the two mould halves may be designed for trimming themould half by means of the one or more support(s) and/or the one orseveral hollow space(s), in order to influence an electromagnetic fieldin the mould cavity. It is thus possible to trim or adjust such a toolretrospectively, i.e. after its manufacture. By this means the tool maybe adjusted individually. The tool may therefore on the one hand bematched to the electrical field provided by an apparatus for theproduction of particle foam parts. On the other hand, the distributionof the electrical field within the mould cavity may be adjustedindividually, i.e. in certain areas the electrical field is intensifiedas compared with other areas if, adjacent to these areas, a trimmingbody is inserted in the hollow space of the mould half. By this meansthe electrical field in the tool may be matched to the geometry of themould cavity.

Furthermore, the electrical field may be matched to the material fromwhich the foam particles are made, which are to be welded into aparticle foam part. Different materials from which the foam particlesare made have differing effects on an applied electrical field. Thus itmay be that the tool in a certain setting functions very well with afirst material, but not with a second material. By replacing ormodifying the arrangement of trimming bodies in the tool, the latter maybe adapted to the second material.

To summarise it may be stated that the electrical field applied in themould cavity is influenced by

-   -   the device which generates the electromagnetic field, as for        example the signal generator and the capacitor plates for an RF        field    -   the shape and material of the mould halves of the moulding tool,        also the material to be welded.

In principle there is the possibility of simulating the electrical fieldin a mould cavity. If however the tool is used in another apparatus toproduce a particle foam part, or a different material is to be welded toproduce it, then in certain circumstances the simulation is no longersuitable. The tool according to the invention may be trimmed or adjustedretrospectively and it may also be adapted subsequently to suitablychanged circumstances (e.g. a different apparatus for production of aparticle foam part or different material to be welded).

For trimming it is for example possible to introduce a dielectricmaterial into the mould half. This dielectric material is polarised byapplying an electrical field so that, in the dielectric material, anelectrical field counteracting the electrical field is generated. Bythis means, the electrical field in the area of the mould cavity isconcentrated and intensified, leading to an enhanced welding effect forwelding the foam particles into a particle foam part.

Preferably the mould half or mould halves has or have at least oneopening leading into the hollow space, so that a trimming body may beinserted in the hollow space. The wall bounding the mould cavity is ofcourse made without an opening. The opening may preferably face the sidefacing away from the mould cavity, but may also preferably face to theside.

The hollow space or at least one of the several hollow spaces may have ashaped or latching element for positioning and/or fixing of a trimmingbody in the hollow space.

Alternatively or additionally, the mould half may have a connection fora trimming fluid which is connected to at least one of the one or morehollow spaces. With this, a trimming fluid may be fed through the hollowspace or spaces or into the hollow space or out of the hollow space.Preferably the hollow spaces are connected to one another for fluidiccommunication, so that the hollow spaces may be fed jointly via a singleor a few, in particular two, connection for trimming fluid. On the otherhand, at least partial volumes of several hollow spaces may beseparated, fluid-tight, from one another, so that the hollow spaces orpartial volumes thereof may be fed individually with trimming fluid. Apartial volume may for example be bounded by a cover located in thehollow space. The cover may be mounted with variable height within thehollow space and may be biased and/or height-adjustable in onedirection.

In addition, at least one connection may be provided for compressed airand/or vacuum, being connected to at least one of the one or more hollowspaces. With this, the hollow space or spaces may be supplied withcompressed air or vacuum, in order for example to press out the trimmingfluid from the hollow space or spaces or to suck it into the hollowspace or spaces. Preferably the connection or connections for compressedair and/or vacuum is or are arranged at a higher level than theconnection or connections for trimming fluid, so that the trimming fluidcan collect in the lower part of the hollow spaces and the compressedair or vacuum connection remains free. Preferably the hollow spaces areconnected through connection openings in the supports, with theconnection openings or a group of connection openings being flush withat least one of the connections for tempering medium, trimming fluid,compressed air or vacuum. The connections for tempering medium, trimmingfluid, compressed air or vacuum may be made in a side wall which closesthe mould half at the side and acts as support. The connection openingsmay be made in bars which run between side walls and act as supports.

A further aspect of the present invention relates to a tool system forthe production of particle foam parts, which includes the tool describedabove and at least one trimming body, which is designed for insertion inthe hollow space or at least one of the hollow spaces, and/or has atrimming fluid provision unit which is designed to supply the mould halfor halves with a trimming fluid.

The trimming body is preferably made from a material with a relativepermittivity (εr) of at least 2. The greater the relative permittivityof the material of the trimming body, the greater its effect as trimmingbody. Materials with a relative permittivity of at least 3 or at least 4may therefore also be expedient. The smaller the relative permittivityof the material of the trimming body, the more precisely and finely theelectrical fields in the mould cavity may be set. Materials with a lowpermittivity, for example less than 2, may therefore also be useful.

The trimming body may be in the form of a plug-in body, which may befixed in the mould half by means of a latching element or by frictionallocking. The trimming body may thus be replaced easily in the mouldhalf, so that the mould half can be adapted to different productionconditions.

The trimming body may be so designed that it fills only a part of thehollow space or spaces. In particular the trimming body is so arrangedin the respective hollow space that it is preferably remote from themould cavity. By this means, the hollow space adjacent to the mouldcavity is, as before, free and may be used for the through passage of atempering medium.

The trimming body may be made of a solid body. In particular thetrimming body may be made of a plastic body. The trimming body mayhowever be made by filling one or more of the hollow spaces with asetting material.

The tool system may also have several trimming bodies, of varying sizeand/or of different materials, having different relative permittivity.

The tool system may also have a connection plate, for mounting between acapacitor plate and a mould half of the tool or on a side of a capacitorplate facing away from a mould half of the tool, and which has mediaconnections and/or media channels and/or media openings for the supplyand or discharge of media for the hollow spaces of the mould half, fromor to the outside. The connection plate may have pipe sections which,when the connection plate is installed according to specification,extend into the hollow spaces of the mould half. The connection platemay be used to introduce media, in particular trimming fluid, into thehollow spaces. Depending on the design, the introduction of media may beeffected jointly into all hollow spaces or individually in specifichollow spaces or groups of hollow spaces.

According to a further aspect of the present invention, a method isprovided for the production of one or more particle foam parts by thewelding of foam particles using electromagnetic waves. This involves atool with mould halves forming a mould cavity arranged between twocapacitor plates. The mould cavity is filled with foam particles, thetool is closed by bringing the two mould halves together, and the toolwith the foam particles is subjected to electromagnetic waves, inparticular radio waves or microwaves, introduced into the mould cavityvia the capacitor plates, wherein the foam particles are heated by theelectromagnetic waves and at least partially fuse or bake together,wherein the method is implemented using the tool or tool systemdescribed above.

At the same time, one or more trimming bodies or a trimming fluid may beprovided in the hollow space or at least one of the hollow spaces, inorder to influence an electromagnetic field in the mould cavity.

It may also be provided, depending on the quality of the welding of thefoam particles, for the arrangement of the one or more trimming bodiesor the trimming fluid in the tool to be changed, in order to adjust theinfluencing of the electromagnetic field in the mould cavity.

It may also be provided for the arrangement of one or more trimmingbodies or the trimming fluid in the tool to be varied during a foamingprocess, in order to have dynamic influence on an electromagnetic fieldin the mould cavity. By this means it is possible to react, inparticular, to changing permittivity of the moulding during the foamingprocess.

If for example it is determined that a particle foam part isincompletely welded in a certain area, then a trimming body may beinserted adjacent to this area, by which means the electrical field inthe mould cavity in which this area is produced, is intensified. If onthe other hand the particle foam part is fused too much at one point,then trimming bodies may be inserted in the trimming wall mould half, inthe other areas adjacent to this point, and the heat output altogetherreduced by means of the electrical field either being applied for ashorter period of time, and/or the electrical field strength (or theelectrical voltage in the case of an RF field applied by means ofcapacitor plates) being reduced.

In conjunction with the setting of the whole electrical power or heatoutput, this method may be used to correct both areas with too muchheating and areas with too little heating.

In trimming, the trimming bodies may also be machined, in order tochange their shape to match the electrical field.

In principle it is also possible to generate locally adapted fields bymeans of capacitor plates which are divided, and height-adjustable inthe individual parts. By means of the present invention it is possible,in a mould cavity of a tool for the production of a particle foam part,to make a local adaptation of the electromagnetic field even forflat-surfaced capacitor plates, which is considerably simpler inproduction and handling.

To summarise, in the tool described above, the shaping tool half is sodesigned that the resulting relative permittivity of the tool coincideswell with the relative permittivity of the particle foam. This isachieved by providing the tool half with free surfaces or volumes (oneor more hollow spaces) either side of the boundary wall and supportssuch as for example walls or bars, where applicable also ribs, posts,honeycombs, zigzag labyrinths, etc. The relation of a volume ofsupporting material and air determines the desired relative permittivityand may for example amount to at least 0.05 or 0.1 and/or up to 0.3 or0.5 or 0.7 or 0.9. If the electromagnetic field is to be intensifiedlocally, for subsequent optimisation of the tool, then trimming bodiesmay be inserted in the hollow spaces. If the supports are in the form ofa labyrinth, then they may already and without further expense be usedas cooling or heating channels. This makes possible variable temperingwith air or CO2 or another tempering medium. The tool according to theinvention facilitates design without simulation, and design rules aresimply defined.

The invention is explained in detail below by way of example, with theaid of the drawings, which show in:

FIG. 1 a sectional view of an embodiment of a tool with two mouldhalves, in a closed position

FIG. 2A a sectional view from above, along a plane indicated by a lineII=II in FIG. 1 , of a top mould half of FIG. 1

FIGS. 2B-2E views of mould half modifications based on FIG. 2A

FIG. 3 an embodiment of a tool system with the tool of FIG. 1 andtrimming bodies

FIGS. 4A and 4B variants of a mould half with trimming bodies in anenlarged view of a detail IV of FIG. 3

FIG. 5 another embodiment of a tool system with the tool of FIG. 1 anddifferent trimming bodies

FIG. 6 another embodiment of a tool with two mould halves in a viewaccording to FIG. 1

FIG. 7 an embodiment of an apparatus for the production of particle foamparts with a tool or tool system of one of the previous representationsin a schematic side view

FIG. 8 an equivalent image of a tool with two mould halves, based oncomparative simulations to determine a field pattern in the tool

FIG. 9 an embodiment of a tool with two mould halves, based on asimulation to determine a field strength pattern in the tool

FIG. 10 a field strength pattern in a simulation with the tool of FIG. 8without trimming bodies

FIG. 11 a field strength pattern in a simulation with the tool accordingto FIG. 12 with trimming bodies

FIG. 12 a sectional view of a further embodiment of a tool with twomould halves, in a closed position.

FIG. 13 a mould half of a tool according to a further embodiment of theinvention

FIG. 14 a mould half of a tool according to yet a further embodiment ofthe invention

FIG. 15 a connection plate for use on a tool according to yet a furtherembodiment of the invention

FIG. 16 a mould half of a tool according to yet a further embodiment ofthe invention

FIG. 17 a mould half of a tool according to yet a further embodiment ofthe invention

FIG. 18A a mould half of a tool with trimming bodies according to a yetfurther embodiment of the invention, in cross-section

FIG. 18B the mould half with trimming bodies of FIG. 18A, viewed fromabove

FIG. 18C the mould half with trimming bodies of FIG. 18A, in anembodiment variant.

A first embodiment of a tool 1 according to the invention for theproduction of a particle foam part has two mould halves 2, 3 (FIG. 1 ).A first mould half 2 (bottom in the Figure) is made of a base 7 and anall-round side wall 8. Provided on the outside of the base 7 is a firstcapacitor plate 4. The other, namely a second mould half 3 (top in theFigure) is made with a boundary wall 10 and an all-round side wall 11and is in the form of a kind of punch, which may be introduced withminimal play into the area bounded by the all-round side wall 8, so thata mould cavity 13 is bounded between the two mould halves 2, 3, whereinthe side wall 11 of the second mould half 3 faces away from the mouldcavity 13. The second mould half 3 is therefore described as the punchmould half 3, and the first mould half 2 as the die mould half 2. On thesame side as the side wall 11, several bars 12 protrude from theboundary wall 10. The bars 12 are joined to the side wall 11 and end ona plane on which lies a second capacitor plate 5. The bars 12 and theside wall 11 of the punch mould half 3 are therefore supports for thepurposes of the invention, serving to support the boundary wall 10 onthe second capacitor plate 5. The second capacitor plate 5 has awaveguide connection 6 for the connection of a waveguide. The side walls11 and bars 12 of the punch mould half 3 form with one another and withthe boundary wall 10 in each case hollow spaces 15, each having anopening 14 at the top. It is therefore to be noted that the hollowspaces 15 face away from the mould cavity 13. The second capacitor plate5 is or may be connected to a piston rod of a press, in order to movethe punch mould half 3 relative to the die mould half 2, and inparticular to insert the punch mould half 3 in the die mould half 2(direction of a framed arrow in FIG. 1 ).

On the side wall 8 of the die mould half 2 is a filler hole 9 forfeeding foam particles into the mould cavity 13 (FIG. 1 ). A vent hole(not shown) may also be provided on the side wall 8, through which aircan escape during filling of the mould cavity 13.

The tool 1 is provided for the production of particle foam parts bywelding of foam particles fed into the mould cavity 13 usingelectromagnetic waves. For this purpose the first capacitor plate 4 maybe connected to ground or earth and the second capacitor plate 5 may beconnected via the waveguide connection 6 to a wave generator. Onconnection of a wave generator such as an RF or microwave generator, ahigh-frequency electromagnetic field is generated in the mould cavity13. Through the energy of the electromagnetic field, the foam particlesare fused and welded together.

The strength of the electromagnetic field prevailing in the mould cavity13 depends on the properties of the materials present between thecapacitor plates 4, 5, and in particular on their relative permittivityεr. The relative permittivity εr is defined as the ratio between thepermittivity of a material or medium and the permittivity of the vacuum,the electromagnetic field constant ε0. The relative permittivity εr ismaterial-dependent and may be understood as a measure of the fieldweakening effects of a dielectric polarisation of the material. Thegreater the relative permittivity εr of a material, the greater thefield weakening.

For air for example the relative permittivity εr lies close to theelectrical field constant ε0, precisely at εr=1.00059. Further examplesof relative permittivity are:

-   -   for Teflon, εr=2    -   for paraffin, εr=2.2    -   for kiln-dried wood, εr=2 . . . 3.5    -   for PE and PET, εr=3.5    -   for PEEK, εr=4    -   for ABS, εr=4.3    -   for porcelain, εr=2 . . . 6    -   for glass, εr=6 . . . 8    -   for tantal pentoxide, εr=27    -   for barium titanate, εr=15,000 (from Helmut Benkert, Einfuerhung        in die Technische Keramik [Introduction to Technical Ceramics],        http://www.keramverband.de/keramik/pdf/02/sem02_03.pdf)        (in each case at roughly 18° C. and 50 Hz, after        https://de.wikipedia.org/wiki/Permittivitaet, unless otherwise        stated). The above examples are intended only as an overview,        and in no way restrict the possible choice of materials for        elements specified in this application, such as for example the        mould halves 2, 3 or the trimming bodies 30, 50 described later.

The mould halves 2, 3 are transparent to (i.e. in principle permeableby) electromagnetic waves, in particular those with a wavelength of thewaves generated by the wave generator. I.e. at least the base 7 of thedie mould half 2 and the boundary wall 10 of the punch mould half 3 aremade from a dielectric which has for example plastic, wood, ceramics,glass or the like. The foam particles fed into the mould cavity 13likewise have dielectric properties. Not only due to irregular geometryof the mould cavity 13, but also with locally differing materials in thefoam particles together with influences from the mould halves 2, 3themselves, it is possible for locally different field strengths of theelectromagnetic field to prevail in the mould cavity 13 and in theparticle foam part to be created, and/or for the energy of theelectromagnetic field to be absorbed with locally varying strength bythe foam particles in the mould cavity 13. Such irregular fieldstrengths and/or absorption rates may be desired, for example becausethe fusing properties of different foam materials may vary, but it mayalso be undesired. This may lead to insufficient or excessive heatingand thus to undesired results in foam particle fusing. To remedy thisproblem, the hollow spaces 15 of the punch mould half 3 are provided,which considerably reduce the mass of material in the punch mould half3. This in turn leads to an advantageous reduction in the influence onthe electromagnetic field strength in the mould cavity 13, whichconsiderably enhances flexibility in use and in shaping of the mouldcavity 13, also of the punch mould half 3. These and other advantageshave already been described at the start of this application, so thatthey are only referred to at this point.

The hollow spaces 15 may also be used for trimming the punch mould half3, in order to influence the electromagnetic field in the mould cavity13. By suitable trimming, the electromagnetic field in the mould cavity13 may be so influenced that an even or otherwise desirable fieldstrength prevails in the mould cavity 13. For example it may bedesirable to have locally differing field strengths in the case oflocally differing particle materials with different relativepermittivity, for locally varying material strengths and locallydifferent material densities. For example it has been found that, atpoints of low material strength (i.e. a low height of the mould cavity13), higher material densities occur due to closing of the tool. Sincecompacted foam particles absorb the applied electromagnetic field morestrongly, such points may be subject to more intensive heating thanadjacent points. It may therefore be observed that, at points of greatercompaction, the foam particles are too strongly fused or even burned orcharred, and/or that welding of the foam particles is inadequate atadjacent points. It may therefore be desirable to have lower fieldstrength at the points of greater compaction of the foam particles thanat adjacent points. The same applies to material mixes with sections ofmore strongly absorbing foam particles and sections of less stronglyabsorbing foam particles. It may also occur that the tool 1 and the foamselection have been matched to one another in advance with the aid ofmodels or tests, but later in series production, variances in fusingbehaviour occur, for example through the use of a modified formulation,or even just another batch of foam particles. In all these cases it maybe desirable to influence the electromagnetic field in the mould cavity13.

For this purpose, trimming bodies 30 may be inserted into the hollowspaces 15 through the openings 14 (FIG. 3 ). The trimming bodies 30 aremade of a dielectric material. Due to the polarising properties of adielectric, the electromagnetic alternating field is weakened by thedielectric lying in the path of the field lines. In areas on the path ofthese same field lines, which are kept free from the dielectric, thefield is on the other hand not weakened, but is even intensified. Theelectrical field may thus be influenced in different ways by means oftrimming bodies 30 of varying size, shape and permittivity.

In order to fix the position of the trimming bodies 30 in the hollowspaces 15, the side walls 8 and bars 12 of the punch mould half 3 mayhave steps 41 in the area of the openings 14, and the trimming bodies 30may have rims 42 or similar shaped features on top, which rest on thesteps 41 on insertion of the trimming bodies 30 (FIG. 4A).Alternatively, the side walls 8 and bars 12 of the punch mould half 3may have latching elements 43 in the area of the openings 14 orthroughout or in other areas, and the trimming bodies 30 may have on theside corresponding shape features which engage with the latchingelements 43 on insertion of the trimming bodies 30 (FIG. 4B).Alternatively, the trimming bodies 30 may be so designed that they areheld in the hollow spaces 15 by simple friction.

Instead of trimming bodies 30 preformed as plug-in bodies as describedabove, trimming bodies 50 may also be formed by introducing a mouldabledielectric material into the hollow spaces 15 (FIG. 5 ). In this case,the trimming bodies 50 may be attached especially easily to the insideof the boundary wall 10. After insertion, the dielectric material of thetrimming bodies 50 may be hardened or adhere with great toughness to thematerial of the second mould half 3.

The trimming bodies 30, 50 are preferably made from a material with arelative permittivity (εr) of at least 2. The greater the relativepermittivity (εr) of the material of the trimming bodies 30, 50, thegreater is their effect on the trimming of the mould half 3, in order toinfluence an electromagnetic field in the mould cavity 13. Consequently,even materials with a relative permittivity (εr) of at least 3 or atleast 4 may be expedient. The lower the relative permittivity (εr) ofthe material of the trimming body, the more precisely and finely theelectrical field in the mould cavity may be set. Materials with a lowrelative permittivity (εr), for example less than 2, may therefore alsobe sensible.

Of course it is conceivable, depending on requirements, that not allhollow spaces 15 are filled with a trimming body 30, 50. It is alsoconceivable that the second mould half 3, on the basis of preliminarytests or simulations, is prepared with primary trimming bodies 30, 50and subsequently, with the aid of actual, possibly changingcircumstances in series production, as shown by the foaming results, isfine-trimmed with secondary trimming bodies 30, 50. Here the primarytrimming bodies may be in the form of trimming bodies 50 of a mouldablecompound (FIG. 5 ), while the secondary trimming bodies are made astrimming bodies 30 with a fixed geometry (FIG. 3 ), or vice-versa, or ineach case one of both. It is also conceivable that a primary trimmingbody 30 of fixed geometry has a further hollow space, in which asecondary trimming body 30, 50 of fixed geometry or of mouldablematerial may be inserted.

In the embodiments described and illustrated, the hollow spaces 15 arefilled only in part with a trimming body 30, 50. As a result it ispossible to use the remaining space for tempering with a temperingmedium. In a further embodiment, the side wall 11 of the punch mouldhalf 3 may have a fluid inflow orifice 61 and a fluid outlet orifice 62and the bars 12 may have fluid throughflow orifices 63 (FIG. 6 ).Provided at the fluid inflow orifice 61 is a fluid flow connection 64which is connected via a valve 66 with a fluid source 67. Provided atthe fluid outlet orifice 62 is a fluid return connection 65which—depending on the fluid used and on process control—leads into theopen air, the environment or, where applicable, via a treatment unit,back to the fluid source 67. Consequently, a tempering fluid may be fedthrough the hollow spaces 15 of the punch mould half 3, in order forexample to preheat the tool 1, to cool the mould cavity 13 or particlefoam bodies contained therein, or quite generally to effect a desiredtemperature control.

Depending on the nature and arrangement of the trimming bodies 30, 50used (cf. FIGS. 3, 5 ), the fluid throughflow orifices 63 may be locatedin the upper area of the hollow spaces 15 or in the lower area of thehollow spaces 15, so that throughflow of the tempering fluid is notimpeded by the trimming bodies 30, 50. If the fluid throughflow orifices63, as in the depicted embodiment, are located in both the upper areaand the lower area of the hollow spaces 15, then different types oftrimming bodies 30, 50 may be used alternatively. The fluid inflow andoutflow orifices 61, 62 are preferably at the height of the fluidthroughflow orifices 63 or, if the fluid throughflow orifices 63 arelocated in both the upper area and also the lower area of the hollowspaces 15, at a height lying between the heights of the fluidthroughflow orifices 63. If a trimming body 30 of fixed geometry is solarge that it extends into the area of the fluid throughflow orifices63, then transverse bores may be provided in such a trimming body 30 atthe height of the fluid throughflow orifices 63. If it should bepossible to fill a trimming body 50 of a mouldable material above theheight of the fluid throughflow orifices 63 into the hollow space, thenit may be advantageous for the fluid inflow and outflow orifices 61, 62and the fluid throughflow orifices 63 to be connected by small pipes orthe like. Even if the fluid inflow and outflow orifices 61, 62 in thedepicted embodiment are provided on opposite sides of the punch mouldhalf 3 and depending on fluid conduction within the punch mould half 3,they may be arranged on the same side or on adjacent sides. To avoid thetempering fluid escaping from the opening 14 of the hollow spaces 15, aseal may be provided on the contact surface of the second capacitorplate 5, wherein the seal may be designed as a boundary seal on the sideof the second mould half 3 or as a flat seal on the side of the secondcapacitor plate 5. Where applicable, the material pairing between thesecond mould half 3 and the second capacitor plate 5 in operation (i.e.under pressure) may also have an adequate sealing effect.

Preferably each of the mould halves 2, 3 is made of a single moulding.Alternatively the side wall 8 of the first mould half 2 may be attachedto the base 7. As a further alternative, the base 7 of the first mouldhalf 2 may be omitted if an adequate seal between the side wall 8 andthe first capacitor plate 4 is ensured in operation (i.e. underpressure). This may be effected by a separately provided seal or by thematerial pairing between the first mould half 2 and the first capacitorplate 4.

According to the embodiment described above, the capacitor plates 4, 5are not part of the tool 1. In a variant embodiment, one or both of thecapacitor plates 4, 5 may be part of the tool 1. For example the base 7of the die mould half 2 may have the first capacitor plate 4, or thefirst capacitor plate 4 may form the base 7 of the die mould half 2. Thefirst capacitor plate 4 may for example be attached to the side wall 8of the die mould half 2 (for example screwed, glued, cast on, etc.) orintegrated in the base 7 of the die mould half 2 (for example cast-in,inserted in a pocket, etc.).

Even if the openings 14 leading into the hollow spaces 15 are providedon the upper edge of the punch mould half 3 in the depicted embodiments,the invention is not restricted to this configuration. Instead, inembodiment variants, the openings 14 may also be provided in a side wall11 of the punch mould half 3, while the top of the punch mould half 3 isclosed. In order to reach, from one side, areas of the punch mould half3 lying further inwards, openings 14 may also be provided in the bars12. In such an embodiment variant, the second capacitor plate 5 may bejoined to the punch mould half 3 or combine with it to form a component.For example the second capacitor plate 5 may be attached to the sidewall 11 of the punch mould half 3 (for example screwed, glued, cast on,etc.) or integrated in a top panel (where present) of the punch mouldhalf 3 (for example cast-in, inserted in a pocket, etc.).

In further embodiment variants it is also conceivable that the sidewalls 8, 11 of the mould halves 2, 3 are made of an electricallyconductive material, and that they are conductively connected to or madeintegral with the capacitor plates 4, 5. If the side walls 8, 11 of bothmould halves 2, 3 are made electrically conductive, then they arecoated, at least in the areas where they contact one another, with anelectrically insulating layer, in particular a plastic coating.

Preferably, in such an embodiment variant, the all-round side wall 8 isnot electrically conductive, e.g. being made of plastic so that, at theboundary zone, no very small spaces occur which would lead to locallyvery strong electrical fields.

It should be noted that the presentation of the geometry of the mouldhalves 2, 3, the mould cavity 13 and the hollow spaces 15 is purely anexample, and depends completely on the nature and shape of a particlefoam body to be produced. If the mould cavity 13 and with it the punchmould half 3 in a top view are for example rectangular, the hollowspaces 15 may likewise be rectangular or square and arranged in themanner of a matrix of for example two rows of four hollow spaces 15(FIG. 2A). As required, the hollow spaces 15 may be more or less closetogether, and the hollow spaces 15 may also have different cross-sectionshapes and sizes. For example the hollow spaces may also be hexagonal(FIG. 2B) in cross-section or circular (FIG. 2C) or more tightly packed(FIG. 2D) or have a different shape. If the mould cavity 13 and with itthe punch mould half 3 in a top view are for example circular or oval,then the hollow spaces 15 may for example be arranged like a piece ofcake (FIG. 2E) or surrounding a circular hollow space 15 in ring-segmentform (FIG. 2F). The cross-section shapes of the mould half 3 shown inthe Figures are entirely exemplary. The mould half 3 may be integralwith the hollow spaces 15 and produced in a single operation, forexample by a casting process. Alternatively, the hollow spaces 15 mayalso be incorporated subsequently in the mould half 3, for example bydrilling out of a complete block. Moreover it is also possible toproduce the mould halves 2, 3 by an additive production process such asthree-dimensional printing, by which means complex shapes with greatvariety may be realised, with or without a minimum of reworking.

Even if, in the depicted embodiments, the hollow spaces 15 are providedin the punch mould half 3, the die mould half (first mould half) 2 maybe provided with hollow spaces in a corresponding manner, in addition oras an alternative to the punch mould half 3.

In addition, in some depicted embodiments, the top capacitor plate 5 isprovided with an all-round edge bar, which surrounds the side wall 11 ofthe punch mould half 3. This edge bar may help to centre and stabilisethe side wall 11, but is entirely optional and may also be omitted.

Even when each of the side walls 8, 11 is described as a singlecontinuous side wall, individual sections of the side walls 8, 11adjacent to one another in the circumferential direction may also bereferred to as side wall.

The tool 1 may be in the form of a crack gap tool, and used as such inoperation in basically three different settings: an open setting (notshown) in which the two mould halves 2, 3 are completely separated fromone another, so that a particle foam part produced with the mouldingtool may be demoulded, an intermediate position (not shown) in which thepunch mould half 3 is inserted so far into the die mould half 2 that themould cavity 13 is closed, but the mould cavity 13 is not yet reduced toits final volume in the closed position (FIGS. 1, 3, 5, 6 ).

In the intermediate position, the filler hole 9 and any vent hole arenot covered by the punch mould half 3, so that these through openingscommunicate with the mould cavity 13 and foam particles may be fed inand/or air discharged. In the intermediate position, the mould cavity 13is filled with foam particles. The punch mould half 3 is then pressed alittle further into the die mould half 2, so that the foam particlescontained therein are compressed.

The tool 1 may be used in an apparatus 70 for the production of particlefoam parts (FIG. 7 ). Such an apparatus has a supply tank 71 which isconnected to the tool 1 by the filler hose 72. The tool 1 is mounted ina press 73 which has a press table 74, a press punch 75, acylinder-piston unit 76 for moving the press punch 75, and a stableframe 77, to which the cylinder-piston unit 76 and the press table 74are fixed. The press punch 75 is made of an electrically conductivemetal plate. Varying from the embodiment of FIG. 1 , in which the secondcapacitor plate 5 has a waveguide connection 6, here the press punch 75is connected via a waveguide 78, e.g. in the form of a coaxial cable, toa wave generator 79. The press table 74 has an electrically conductivetable top made of metal, which is connected to earth via an electricallyconductive baseplate.

The use of the tool 1 to produce a particle foam part in the apparatus70 is described below.

The tool 1 is, to begin with, in an intermediate position. Here thepunch mould half 3 is inserted so far into the die mould half 2 that themould cavity 13 is substantially closed. In this intermediate positionthe tool 1 is inserted in the press 73. The filler hose 72 is connectedto the filler hole 9 of the tool 1.

Foam particles from the supply tank 71 are fed to the mould cavity 13.When the mould cavity 13 is completely filled with foam particles, thenthe cylinder-piston unit 76 is actuated, in order to press together thetwo clamping platens 13, 16 and with them the two mould halves 2, 3.

The tool 1 is thus brought into the closed position. By this means thefoam particles present in the mould cavity 13 are compressed.

On pressing together of the two mould halves 2, 3, the filler hole 9 ofthe die mould half 2 is covered by the punch mould half 3 and therebyclosed. The filler hose 72 may then be removed from the tool 1. A plugmay then be inserted in the filler hole 9 and has a similar dielectricconstant to the side wall 8.

In the pressed-together or closed state of the tool 1, the wavegenerator 79 is used to generate an electromagnetic high-frequencysignal (RF or microwave signal) which is applied via the waveguide 78 tothe press punch 75 at the top capacitor plate 5 of the punch mould half3. The waveguide 78 may be hollow and may have a core. The bottomcapacitor plate 4 of the die mould half 2 is connected to earth via thepress table 74. The capacitor plates 4, 5 are insulated from one anotherelectrically by the electrically non-conductive base body of the mouldhalves 2, 3, so that they form a plate capacitor, which encompasses themould cavity 13. By means of the electromagnetic field thus generated,the foam particles are heated and welded together into a particle foampart.

The press 73 can be opened so that the tool 1 may be removed. If thetool has locking devices, it may be removed in the closed state. It maythen be cooled by means of a suitable cooling device, for example a fan.While the tool 1 in which a particle foam part has already been formedis cooled, a further tool 1 may be inserted in the press 73.

When the particle foam part has been sufficiently cooled, the two mouldhalves 2, 3 are if necessary loosened, the punch mould half 3 is lifted,and the particle foam part may be suitably demoulded.

The capacitor plates 4, 5 are in this embodiment part of the apparatus70 and may be used for a variety of tools 1. They are also used inparticular as press plates in the apparatus 70. In this connection it isalso irrelevant whether the tool 1 is inserted between the capacitorplates 4, 5 in the orientation shown in FIG. 1 , etc. from above andbelow or vice-versa.

The tool according to the invention may be modified in a variety ofways. In a tool 1 according to a further embodiment, both mould halves2, 3 are made with hollow spaces 15 for trimming the respective mouldhalves, in order to influence an electromagnetic field within the mouldcavity 13 (FIG. 12 ). In this embodiment the first mould half 2 in thisrespect is basically analogous in form to the second mould half 3, sothat the bars 12 and side wall 8 of the first mould half 2 form supportsfor the first capacitor plate 4.

Also in this embodiment the bars 12 are not integral with the mouldhalves 2, 3 as in previous embodiments, but are inserted as independentcomponents in suitable slots in the side of the boundary walls 10 facingthe mould cavity 13. Where applicable, corresponding slots, runningvertically, may also be provided in the inner faces of the side walls 8,11 of the mould halves 2, 3, in order to stabilise the bars 12.Alternatively or in addition, the bars 12 may also be bonded or weldedon, or wedged between the side walls 8, 11.

The invention is also not restricted to the crack gap process. In thecase of the tool 1 of this embodiment, the mould halves 2, 3 are notdesigned as punch and die, but instead abut one another at the ends withtheir side walls 8, 11. For this purpose the side walls 8, 11 havematching steps 120, in order to seal the mould cavity 13 as processpressure builds up. The tool 1 of this embodiment also has a filler hole121 which, with the tool 1 closed, remains open and to which may beconnected a filling injector 122, by which the foam particles are fedinto the mould cavity 13.

Apart from the above modifications, what has been said previously forall other embodiments and their variants and modifications appliesanalogously, as far as basically applicable. Also the abovemodifications, not only in their totality but also modifications takenindividually of any other embodiment and its variants and modificationsof other independent variants, as far as basically applicable.

The inventors of the present application have made simulations of theeffect of the present invention. To begin with, a simplified model asconsidered with the aid of an equivalent image (FIG. 8 ). This involvedthe capacitor plates 4, 5 being connected to a voltage source 80,corresponding to a polarisation state of the wave generator 79. Thus thecapacitor plates 4, 5 are oppositely charged. Between the capacitorplates 4, 5 are to be found several areas 81, 82, 83, each withdifferent, where applicable also locally distributed, dielectricproperties. For the simulation, at least three areas are required, ofwhich a first area 81 corresponds to the mould cavity 13, a second area82 corresponds to the boundary wall 10 and a third area 83 correspondsto a hollow space 15 of the tool 1. Under this specification, anelectromagnetic field E forms between the capacitor plates 4, 5, withits strength depending on the relative permittivity of the areas 81, 82,83. Using this model, field strength patterns of the electromagneticfield E between the capacitor plates 4, 5 may be calculated. Furtherareas may be defined as required or for further approximation tospecific forms of the tool 1 and of a tool system with trimming bodies.

For example one model provides in section two side walls 8 of the firstmould half 2 (FIG. 9 ), extending between the capacitor plates 4, 5. Abase (reference number 7 in FIGS. 1, 3, 5, 6 ) is not provided in thismodel. In this model, the capacitor plates 4, 5 extend sideways over theside wall 8 of the first mould half 2. The first capacitor plate 4 isearthed, the second capacitor plate 5 is connected to a wave generator79. Between the side walls 8, a boundary wall 10 of the second mouldhalf 3 extends in an oblique straight line. From the boundary wall 10,side walls 11 and bars 12 (i.e. supports 11, 12 for the purposes of theinvention) lead to the second capacitor plate 5, in order to allowhollow spaces 15 between them (in section six hollow spaces 15, withoutrestricting the generality). Defined between the first capacitor plate4, the side walls 8 of the first mould half 2 and the boundary wall 10is a mould cavity 13, which in this model is wedge-shaped. The sidewalls 8, 11, boundary wall 10 and bars 12 are of roughly equal strength,have a relative permittivity or around εr=3.2 and abut one another at anangle. The mould cavity 13 and the hollow spaces 15 are initially empty(i.e. filled with air, εr=1).

This model was subjected to a simulation of field strength distribution(FIG. 10 ). This involved the generation, by means of the wave generator79, of an electromagnetic field E between the capacitor plates 5, 6,which without disturbances has a field strength of |E|=1.5 E5 V/m. Inthe Figure, contour lines are plotted in gradations of around 0.25 E5V/m. Of course, the transitions of field strength are not stepped, butfluid. It is shown that field strength declines within the boundary wall10 to around 0.75 E5 V/m, with the lowest field strength occurring atparts of the boundary wall 10 which bound the hollow spaces 15, whilethe field strength in parts of the boundary wall 10 which bordersupports 11, 12 is somewhat higher. Within the supports 11, 12, as alsothe side wall 8 of the first mould half 2, apart from the points atwhich they abut the boundary wall 10, the field weakening is negligible.Within the mould cavity 13, at the points lying opposite the supports11, 12, a locally tightly restricted increase in field strength occurs,similarly at the base of the hollow spaces 15. However this effect isextremely slight. This is associated with the fact that the fieldweakening within the supports 11, 12 is, as stated above, negligible.

The practically disappearing field weakening in the supports 11, 12 isat first surprising. On account of the dielectric properties, a fieldweakening of the order of magnitude of the boundary wall 10 would beexpected. Such a field weakening in the supports 11, 12 would also leadto a marked lack of homogeneity of the field in the mould cavity 13 ascompared with the supports 11, 12, and would be difficult to handle. Theinventors of the present invention have however established, throughtheoretical considerations, simulations and tests, that such an effectis not present, which makes execution of the invention stillpracticable. A theoretical explanation for this behaviour is possible ifone divides the arrangement between the capacitor plates 4, 5 into smallelements in the lateral direction, and then considers the elements,first of all individually, and then superimposed. If one such elementcontains a support 11, 12 of a dielectric material, a field weakeningwould actually occur there. This is however superimposed andextinguished by a field strengthening which occurs in the boundary zoneof an adjacent element (i.e. extending to the side over the adjacentelement).

On the basis of the same model, a further simulation was conducted, inwhich the hollow spaces 15 were filled completely with a dielectrichaving relative permittivity of around εr=3.2, and the mould cavity 13was completely filled with a dielectric with a relative permittivity ofaround εr=1.3 (FIG. 11 ). It revealed a marked weakening of the field inthe whole area of the second mould half 3 (more precisely, in theleft-hand higher area a lower weakening to around 1 to 1.25 E5 V/m, andin the right-hand less high area the greatest weakening, to around 0.75E5 V/m) and a distinct strengthening of the field in the whole area ofthe mould cavity 13 (more precisely, in the left-hand less high area thegreatest strengthening to over 2.5 E5 V/m, and in the right-hand higherside a lesser strengthening to around 1.75 to 2 E5 V/m).

It has been shown above, that in a tool for the production of particlefoam parts by welding of foam particles using electromagnetic waves, astructure of a mould half of a dielectric material with a boundary wall10 to the mould cavity 13 and supports 11, 12 which form hollow spaces15 on the side facing away from the mould cavity, make it possible toproduce in the mould cavity 13 an electromagnetic field with goodhomogeneity. Through the optional, targeted and selective introductionof trimming bodies 30, 50 into the hollow spaces 15, the mould half andthus the tool become capable of trimming in the sense that anelectromagnetic field in the mould cavity 13 may be influenced in atargeted manner.

A development of the invention provides as further embodiment that thetrimming of the mould half may be varied during a foaming process. Thefoaming process here covers a period from introduction of the foamparticles to removal of the particle foam part. Naturally this does notrule out changes to trimming before and/or after the foaming process.For this purpose a trimming body in the form of a fluid is used and thisfluid is fed via trimming fluid lines to the hollow space or spacesand/or carried away from the hollow space or spaces. The mould halfand/or the associated capacitor plate is or are so designed that thismay also occur during a foaming process, i.e. in particular with thetool mounted between the capacitor plates and/or with the mould cavityclosed. Alternatively or additionally, the supply/removal of thetrimming fluid may also be effected via a trimming fluid supply unitlocated between the mould half and the capacitor plate. For examplewater, oil or a viscous fluid (e.g. gel) may be used as trimming fluid.Preferably chosen as trimming fluid is a fluid with a low relativepermittivity. In this embodiment it is possible to compensate for achange in relative permittivity due to escape of water (vapour) from themould cavity 13 in the course of the foaming process through targetedintroduction or removal of trimming fluid into or from the hollow spaces15.

In one embodiment, bores 130 are provided in the side walls 11 and thebars 12, and connect the hollow spaces 15 in the second mould half 3 forcommunication purposes (FIG. 13 ). In the depicted variant, each of thebores 130 is made from one side through a side wall 11, continuouslyover the whole length or width of the mould half 3, through all bars 12lying in one line, up to the last hollow space 15 lying on the line, andform in each case at least one opening 131 in a side wall 11. Attachedat one of the openings 131 is a trimming fluid feed connection 132 withvalve, which is connected to a trimming fluid supply tank 134 via a feedpump 133. Attached to another of the openings 131 is a trimming fluiddischarge connection 135 with valve, which is connected to the trimmingfluid feed pump 133 via a trimming fluid drain pump 136. Attached toanother of the openings 131 is an incoming air connection 137 withvalve, while a vent connection 138 with valve is attached to a last ofthe openings 131. The incoming air connection 137 and the ventingconnection may each be equipped with a fluid lock. The incoming airconnection 137 may be connected to a compressed air tank or an airsupply pump, and the venting connection 138 may be connected to a vacuumtank or a vacuum pump.

To fill the hollow spaces 15 with the trimming fluid, the trimming fluidfeed connection 132 and the venting connection 138 are opened and thefeed pump 133 is set in operation, in order to feed trimming fluid fromthe trimming fluid supply tank 134 into the hollow spaces 15. Due to thecommunicating connection via the bores 130, all hollow spaces 15 arereached. Surplus air can escape through the venting connection 138. Whenthe hollow spaces 15 are filled with a predetermined amount of trimmingfluid, the trimming fluid feed connection 132 and the venting connection138 are closed and the feed pump 133 is switched off. The amount oftrimming fluid may be determined in advance. Reaching of thepredetermined amount may be determined for example by a flow measurementat the feed pump 133, or ensured by design of the latter as a meteringpump. Alternatively, complete filling of the hollow spaces 15 may bedetected by triggering a fluid lock of the venting connection 138.

To empty the hollow spaces 15, the trimming fluid discharge connection135 and the incoming air connection 137 are opened, and the trimmingfluid drain pump 136 is put into operation, in order to withdrawtrimming fluid from the mould half 3 and return it to the trimming fluidsupply tank 134. The trimming fluid may therefore also be moved in acircuit. Because of the communicating connection of the bores 130, allhollow spaces 15 are reached. The hollow spaces 15 may be keptunpressurised via the incoming air connection 137, or the removal oftrimming fluid may be assisted by compressed air. When the hollow spaces15 have been emptied, the trimming fluid discharge connection 135 andthe incoming air connection 137 are closed and the trimming fluid drainpump 136 is switched off.

The trimming fluid feed connection 132 and/or the trimming fluiddischarge connection 135 may each be designed optionally without avalve, if the respective pump 133, 136 has suitable locking devices.Optionally, the pumps 133, 136 may be integrated with the respectivetrimming fluid connections 132, 135, or attached to the latter, or thevalves of the trimming fluid connections 132, 135 may be integrated withor attached to the respective pumps 133, 136.

In the depicted embodiment variant, each bore 130 ends in the lasthollow space 15 lying on the bore line. Alternatively, the bores 130 mayalso pass via the last hollow space 15 through the adjacent side wall11. This increases the connection options and in this way alsofacilitates adaptation to circumstances on the equipment side. Openingsin the side walls 11 which are not required may be closed by blindplugs.

In one embodiment variant the bores 130 may be made on a first planerelative to a height of the mould half 3, and further bores (notexplicitly shown) may be made on a second higher plane, wherein thetrimming fluid connections 132, 135 are connected to the openings 131 onthe first plane, and the incoming air connection 137 and the ventingconnection 138 are connected on the second plane. Openings in the sidewalls 11 which are not required are then closed by blind plugs.

Instead of bores, in production of the mould half 3, an additiveproduction process may be used to provide apertures in the side walls 11and the bars 12. At the same time, additional connections may also bemade in the bars 12, without the need for a bore from the outside. Thismay also avoid the need for unnecessary openings in the side walls 11.

In a further embodiment, covers 140 are provided in each of the hollowspaces 15 of the top mould half 3, dividing each hollow space into atrimming chamber 142 below the cover 140 and a pressure chamber 141above the cover 140 (FIG. 14 ). The covers 140 are pushed upwards byrespective compression springs 148 mounted in the trimming chamber 142.Through respective bores in the covers 140 and in the capacitor plate 5bordering the top mould half 3, trimming fluid lines 143 extend into thetrimming chamber 142 of each hollow space 15. The trimming fluid lines143 run together outside the tool and are connected to a trimming fluidvalve 144, here in the form of a directional valve. Through the trimmingfluid valve 144, in a first switching position, trimming fluid may befed via a trimming fluid feed pump 133 from a trimming fluid supply tank134 into the trimming fluid line 143. In a second switching position,the trimming fluid line 143 is connected to a return line in thetrimming fluid supply tank 134. In a third switching position (neutralposition), all connections of the trimming fluid valve 144 are blocked.Through further bores in the capacitor plate 5, compressed air lines 145extend into the pressure chamber 141 of each hollow space 15. Thecompressed air lines 145 converge outside the tool and are connected toa compressed air valve 146, which is here in the form of a directionalvalve. In a first switching position (neutral position), the compressedair line 145 is connected to atmosphere. In a second switching position,the compressed air line 145 is connected to a compressed air tank 147.

To fill the hollow spaces 15 with trimming fluid, the trimming fluidvalve 144 is switched from the neutral position into the first switchingposition, wherein the compressed air valve 146 in the first switchingposition is connected to atmosphere, and the feed pump 133 is set inoperation to feed trimming fluid from the trimming fluid supply tank 134through the trimming fluid lines 143 into the trimming chambers in thehollow spaces 15. Because of the individual connection via the trimmingfluid lines 143 with the trimming fluid feed pump 133, all hollow spaces15 are filled quickly and simultaneously with trimming fluid. Surplusair can escape via the compressed air valve 146 when the covers 140 inthe hollow spaces 15 are pressed upwards. When the hollow spaces 15 arefilled with a predetermined amount of trimming fluid, the trimming fluidvalve 144 is switched into the neutral position, thereby blocking anyflow of trimming fluid, and the feed pump 133 is switched off. Throughthe action of the compression spring 148, which presses the covers 140upwards, the amount of trimming fluid may be equalised between theindividual hollow spaces 15. Reaching of the predetermined amount may bedetermined for example by a flow measurement at the feed pump 133 orensured by design of the latter as a metering pump.

To empty the hollow spaces 15, the trimming fluid valve 144 is switchedinto the second switching position, and the compressed air valve isswitched into the second switching position in order to supply thepressure chambers 141 of the hollow spaces 15 with compressed air. Thecompressed air in the pressure chambers 141 presses the covers 140 down,so that the trimming fluid in the trimming chambers 142 is pressed intothe trimming fluid lines 143 and out of the mould half 3, and isreturned to the trimming fluid supply tank 134. Consequently thetrimming fluid too may also be circulated. Due to the individualconnection via the compressed air lines 145 with the compressed air tank147, all hollow spaces 15 are emptied simultaneously and quickly. Whenthis process has been completed, the trimming fluid valve 144 isswitched into the neutral position and the compressed air valve 146again connected to atmosphere.

In a modification (not shown in detail), the trimming fluid lines 143may be connected individually to respective trimming fluid valves foreach hollow space 15. The trimming fluid valves may be attached to thecapacitor plate 5, or accommodated or combined in a separate controlunit. Here the trimming fluid valves may be of the same design as thetrimming fluid valve 144 and connected by the respective differentroutes with the trimming fluid feed pump 133 via a common trimming fluidfeed line, or with the trimming fluid supply tank 134 via a commontrimming fluid return line.

In a further modification (not shown in detail), the compressed airlines 145 may be connected individually to respective compressed airvalves for each hollow space 15. The compressed air valves may beattached to the capacitor plate 5, or accommodated or combined in aseparate control unit. Here the compressed air valves may be of the samedesign as the compressed air valve 146 and connected by the respectivedifferent routes with the compressed air tank 147 via a commoncompressed air line or, if applicable, connected to atmosphere via acommon venting line.

In a further modification (not shown in detail), sections of thetrimming fluid lines 143 and/or the compressed air lines 145 may beattached separately to an inside and/or an outside of the capacitorplate 5. At the same time the bores in the capacitor plate 5 may beprovided for example with threads, so that an inner part of the trimmingfluid lines 143 and/or the compressed air lines 145 may be screwed tothe inside of the capacitor plate 5, and an outer part of the trimmingfluid lines 143 and/or the compressed air lines 145 may be screwed tothe outside of the capacitor plate 5. For example, an inner part of thetrimming fluid lines 143 may be a pipe section with a threaded end.Moreover, an inner part of the trimming fluid lines 143 may be ofvarying length, depending on the depth of the hollow space 15 to besupplied.

In a development of the last-mentioned modification, a connection plate(not shown in detail) may be provided, carrying sections of the trimmingfluid lines 143 and/or the compressed air lines 145 facing into thehollow spaces 15. The sections of the trimming fluid lines 143 may herefor example be in the form of pipe sections, which are firmly joined tothe connection plate or may be attached to it, for example using screws,insertion or bonding in suitable bores. The sections of the compressedair lines 145 may be designed in a similar manner and attached or besimple openings of corresponding bores, since the compressed air lines145 need not extend into the hollow spaces 15. At the same time, boresin the capacitor plate 5 may line up with bores in the intermediateplate, so that sections of the trimming fluid lines 143 and/or thecompressed air lines 145 which are attached to the connection plate, maybe inserted from the outside, through the bores, into the capacitorplate 5, so that a reliable alignment of the connection plate and thecapacitor plate is also ensured. The outer parts of the trimming fluidlines 143 and the compressed air lines 145 are then to be attached tothe outside of the connection plate. The connection plate may be madefor example of metal or plastic. The connection plate may be madeconventionally by providing a plate and pipes, where applicable withsuitable machining and assembly. Alternatively, the connection plateincluding any pipes of the lines 143, 145 may be made in one piece by anadditive production process.

In one variant, the connection plate is/may be located between the mouldhalf 3 and the capacitor plate 5. In this case too, bores in thecapacitor plate 5 may be aligned with bores in the intermediate plate.Then, however, the outer-lying parts of the trimming fluid lines 143 andthe compressed air lines 145 are to be attached to the outside of thecapacitor plate 5. In addition, in this variant, short pipe sections maybe located as sections of the compressed air lines 145 on the outside ofthe connection plate, and may be insertable into the corresponding boresof the capacitor plate so that in this case too, a reliable alignment ofthe connection plate and the capacitor plate is ensured. If theconnection plate of this variant is made of metal, it may act as afunctional part of the capacitor plate 5 in respect of the generation ofthe electromagnetic field.

If the connection plate of this variant is made of plastic, it cancontribute to the dielectric effect of mould half 3.

In a further modification, it is possible to provide a connection plate150 (FIG. 15 ), which holds or has sections of the trimming fluid lines143 and the compressed air lines 145, wherein the sections of the lines143, 145 facing towards the mould half open in the surface of theconnection plate 150 and the outwards-facing sections of the lines 143,145 open at a side edge or several side edges of the connection plate150. A switch unit with valves may also be provided there. Specifically,the connection plate 150 may have a cuboid shape with an inner surface151, an outer surface 152 opposite the former, a first side face 153which connects the inner surface 151 and the outer surface 152, a secondside face 154 which adjoins the first side face 153, and other sidefaces which lie opposite the first side face 153 and second side face154 respectively. The inner surface 151 has a first group of bores 155,each carrying a pipe section 156, and a second group of bores 157. Thefirst side face 153 carries in a plane close to the outer surface 152 agroup of third bores 158, each meeting on a row of the first group ofbores 155. The second side face 154 carries in a plane close to theinner surface 151 a group of fourth bores 159, each meeting on a row ofthe second group of bores 157. The first group of bores 155 is offsetdiagonally relative to the second group of bores 157, and the thirdgroup of bores 158 is offset vertically relative to the fourth group ofbores 159, so that the bores 155 of the first group communicate onlywith bores 158 of the third group and vice-versa, and the bores 157 ofthe second group communicate only with bores 159 of the fourth group andvice-versa. Thus the bores 155 of the first group with pipe sections 156and the bores 158 of the third group respectively form sections of thetrimming fluid line 143, and the bores 157 of the second group and thebores 159 of the fourth group respectively form sections of thecompressed air line 145 (cf. FIG. 14 ), and the trimming fluid line 143has no overlaps with the compressed air line 145.

The openings of the bores 158, 159 may be connected to one another byrespective line sections or connection units. All bores 155, 157, 158,159 are preferably in the form of blind holes. If they are in the formof through bores, one side of each should be closed by blind plugs.

Although not shown in detail, the bores 158 of the third group may beconnected to one another by a first collective bore in the second sideface 154 or the side face lying opposite the former, and the bores 159of the fourth group may be connected to one another by a secondcollective bore in the first side face 153 or the side face lyingopposite the former. The bores 158, 159 of the third and fourth groupsmay then be closed by blind plugs, and only the first collective boreneed be connected to the trimming fluid valve 144 and the secondcollective bore to the compressed air valve 146.

It goes without saying that the specific arrangement of the bores 155,157, 158, 159 in FIG. 15 is to be understood as purely exemplary. Inparticular, the bores 158, 159 of the third and fourth groups may alsobe made on a single side face 153 or 154, in that case even on a singleplane, without the occurrence of overlaps between the trimming fluidline 143 and the compressed air line 145. The arrangement shown in FIG.15 has however the advantage that the media trimming fluid andcompressed air are separated from one another from the technicalconnection standpoint.

Otherwise, the explanations made in respect of the connection platedescribed earlier, with regard to layout, material and method ofproduction may be transferred equally to the connection plate 150described here.

In a further modification, a cover plate 160 may also be provided. Thisis arranged between the mould half 3 and the capacitor plate 5 and hasseveral projections which extend into the hollow spaces 15 and limittheir volume (FIG. 16 ). Analogous to the arrangement shown in FIG. 13 ,one or more bores 130 may be provided in the top mould half 3, formingin at least one side wall 11 a connection opening for trimming fluid andcutting through at least one of the bars 12, in order to connect severalhollow spaces 15 of the mould half 3 with fluidic communication. Thearrangement of the bores may be in principle as desired, so long astrimming fluid may be fed to and removed from, or directed through, allhollow spaces. The projections 161 are preferably so dimensioned thatthe volumes remaining in the hollow spaces 15 are substantially of equalheight, but this too is optional and may be adapted to requirements. Invariants, the projections 161 may be interchangeable elements ofdifferent height, which can be attached to the cover plate. The bore orbores 130 is or are so designed that they lie in the range of thevolumes left by the projections 161, and in addition in such a way thatall volumes remaining in the hollow spaces 15 may be filled withtrimming fluid and as far as possible completely emptied afterwards.Thus for example in FIG. 16 an opening made through the bore 130 at thetop of the right-hand side wall 11 may serve as a feed connection fortrimming fluid, and an opening made through the bore 130 at the bottomof the left-hand side wall 11 may serve as a discharge connection fortrimming fluid, so that gravity may be utilised in both supply andremoval of the trimming fluid. The cover plate 160 may in principle bemade by a casting process, by deep-drawing a plate, by milling outand/or drilling from a solid piece or by an additive process. In thecase of an additive process (3D printing), no bores are necessary, butinstead all connection openings may be made in one go with the additiveformation of the cover plate 160.

In a further embodiment, covers 170 may be provided, each arranged inone of the hollow spaces 15 with vertical movement facility andindividually height-adjustable via a tappet 171 and a lifting drive 172attached to the top capacitor plate 5 (FIG. 17 ). The tappets 171 aremounted in bores 173 of the top capacitor plate. The tappets 171 may bein the form of threaded rods, screwed into bores 173 provided withinside thread, and may be turned by the lifting drive 172 in the form ofa rotary drive via a driving slot (not shown in detail), so that byturning in the (threaded) bores 173 an adjustment in height may beeffected. Other facilities for height adjustment are well-known in thetechnology and may be used alternatively, depending on requirements. Asin FIG. 17 , at least one bore 130 is provided to supply the hollowspaces 15 with trimming fluid; in this respect the explanations givenabove apply. Through the height-adjustment, the covers are able todelimit the volume of the hollow spaces 15 individually (FIG. 16 ).Thus, the relative permittivity of the mould halves may not only bematched locally, but may also be varied in the course of the foamingprocess. In addition, expelling of the trimming fluid through the bore130 may also be assisted by closing of the cover.

Naturally, everything described above relating to the top mould half 3is applicable correspondingly and analogously to the bottom mould half2.

According to a further embodiment, one of the mould halves 2, 3 may alsohave a side opening or several side openings 14, into which a mould body30 may be inserted and removed from the side (FIG. 18A, direction ofmovement 180). The mould body 30 may be comb-shaped with a base 181 andseveral cuboid prongs 182 (FIG. 18B). Alternatively, several individualcuboid mould bodies 30 may be used which, if applicable, may be movedinto and out of the hollow spaces 15 under individual control. A toolsystem with such mould halves 2, 3 and mould bodies 30 is especially,but not only, suitable for the production of particle foam part with theaid of electromagnetic waves. In a development, several mould bodies 30in the form of plates of the same shape as described above, but of lowerheight, may be provided; together they fill the hollow spaces 15 and maybe moved into and out of the hollow spaces 15 under individual control(FIG. 18C).

Pumps 133, 136, connections 132, 135, 137, 138, valves 144, 146, tanks134, 147, lines 143, 145 and other pipework may be, individually and inany arrangement and/or sub-combination, part of a trimming fluid supplysystem. A control unit for control of all process operations describedincluding the activation of motors, pumps, valves, and the provision ofsuitable sensors to provide process and status data for the control unitas required, are a matter of course and need no further explanation.

The invention has been described completely above with the aid ofembodiments. The invention is however defined only by the appendedindependent claims and is further developed by the dependent claims. Tothe extent that the embodiments contain individual features which gobeyond the dependent claims, these are for illustration only, but arenot intended to limit the invention, even if they may contain furtherinventive ideas. All features which are described in relation to anembodiment, a variant, alternative or option, are also to be related toall other embodiments, variants, alternatives or options, unless clearlyexcluded. In addition, all features which are described in relation toan embodiment, a variant, alternative or option, also individually or inany desired sub-combination with one another and/or with features ofother embodiments, variants, alternatives or options, define in eachcase independent subjects of the invention.

LIST OF REFERENCE NUMBERS

-   1 tool-   2 first (bottom) mould half (die mould half)-   3 second (top) mould half (punch mould half)-   4 first capacitor plate (bottom capacitor plate)-   5 second capacitor plate (top capacitor plate)-   6 waveguide connection-   7 base-   8 side wall-   9 filler hole-   10 boundary wall-   11 side walls (support)-   12 bar (support)-   13 mould cavity-   14 opening-   15 hollow space-   30 trimming body-   41 step-   42 rim-   42 latching arrangement-   50 trimming body-   61 fluid inflow orifice-   62 fluid outlet orifice-   63 fluid throughflow orifice-   64 fluid flow connection-   65 fluid return connection-   66 valve-   67 fluid source-   70 apparatus-   71 supply tank-   72 filler hose-   73 press-   74 press table-   75 press punch-   76 cylinder-piston unit-   77 frame-   78 waveguide-   79 wave generator-   80 voltage source-   81-83 areas-   130 bore-   131 opening-   132 trimming fluid feed connection (valve)-   133 trimming fluid feed pump-   134 trimming fluid supply tank-   135 trimming fluid discharge connection (valve)-   136 trimming fluid drain pump-   137 incoming air connection (valve)-   138 venting connection (valve)-   140 cover-   141 pressure chamber-   142 trimming chamber-   143 trimming fluid line-   144 trimming fluid valve-   145 compressed air line-   146 compressed air valve-   147 compressed air tank-   148 compression spring-   150 connection plate-   151 inner surface (to tool)-   152 outer surface (to capacitor plate)-   153, 154 side faces-   155 bore (first group)-   156 pipe section-   157 bore (second group)-   158 bore (third group)-   159 bore (fourth (group)-   160 cover plate-   161 projection-   170 cover-   171 tappet-   172 lifting drive-   173 bore

The above list is an integral part of the description.

The invention claimed is:
 1. A tool for production of particle foamparts through welding of foam particles by means of electromagneticwaves, comprising two mould halves which bound a mould cavity, whereinat least one of the two mould halves is made of a material which istransparent to electromagnetic waves and has a boundary wall whichbounds the mould cavity and one or more supports serving to support theboundary wall on a capacitor plate on a side facing away from the mouldcavity and forming one or more hollow spaces between the boundary walland the capacitor plate, and wherein a relation of a volume of the oneor more supports and air within the one or more hollow spaces of the twomould halves is adjusted such that a resulting relative permittivity ofthe tool is adapted to a relative permittivity of the foam particles,such that a temperature in the foam particles is levelled as a whole orcan be locally adjusted at need.
 2. The tool according to claim 1,wherein the boundary wall is made with substantially constant thickness.3. The tool according to claim 1, wherein the one or more supports runroughly parallel to a pressing direction, in which the two mould halvesin operation are pressed together by a press.
 4. The tool according toclaim 1, wherein the tool has connections for a tempering medium, whichmay flow through the one or more hollow spaces.
 5. The tool according toclaim 1, wherein at least one of the two mould halves is designed fortrimming the mould half by means of the one or more supports and/or theone or more hollow spaces, in order to influence an electromagneticfield in the mould cavity.
 6. The tool according to claim 1, wherein theone or more hollow spaces has an opening, through which a trimming bodymay be inserted into the one or more hollow spaces.
 7. The toolaccording to claim 6, wherein the opening faces the side facing awayfrom the mould cavity.
 8. The tool according to claim 6, wherein the oneor more hollow spaces has a shaped or latching element for positioningand/or fixing a trimming body in the one or more hollow spaces.
 9. Thetool according to claim 1, wherein the two mould halves have at leastone connection for a trimming fluid, in particular liquid or oily orviscous, which is connected to at least one of the one or more hollowspaces, are connected for fluidic communication with one another, or atleast part-volumes of several hollow spaces are separated from oneanother with fluid-tightness.
 10. The tool according to claim 9, whereinthe two mould halves have at least one connection for compressed airand/or vacuum, which is connected to at least one of the one or morehollow spaces, wherein the connection or connections for compressed airand/or vacuum is or are arranged on a higher plane than the connectionor connections for trimming fluid.
 11. The tool according to claim 4,wherein the one or more hollow spaces are connected through connectionopenings in the one or more supports, wherein the connection openings ora group of connection openings are preferably flush with at least one ofthe connections made in a side wall for tempering medium, trimmingfluid, compressed air or vacuum.
 12. The tool according to claim 1,wherein each of the two mould halves is made of a material transparentto electromagnetic waves, and has the boundary wall and the one or moresupports.
 13. A tool system for the production of particle foam parts,wherein the tool system includes a tool according to claim 1, and atleast one trimming body which is designed for insertion in the one ormore hollow spaces, and/or a has trimming fluid provision device whichis designed to supply the mould halves with trimming fluid.
 14. The toolsystem according to claim 13, wherein the at least one trimming body ismade of a material with a relative permittivity (εr) of at least
 2. 15.The tool system according to claim 13, wherein the at least one trimmingbody is made from a solid body or is produced by pouring a settingmaterial into the one or more hollow spaces.
 16. The tool systemaccording to claim 13, wherein the at least one trimming body isdesigned as a plug-in body for plugging into the one or more hollowspaces.
 17. The tool system according to claim 16, wherein the at leastone trimming body has a shaped element or a latching element forpositioning and/or fixing in the one or more hollow spaces, or may befixed by frictional locking in the one or more hollow spaces.
 18. Thetool system according to claim 13, wherein the at least one trimmingbody is designed that it fills only a partial area of the one or morehollow spaces, wherein the partial area is preferably a partial arealocated away from the mould cavity.
 19. The tool system according toclaim 13, wherein the tool system includes trimming bodies of differingsize and/or of different materials which have differing relativepermittivity (εr).
 20. The tool system according to claim 13, whereinthe tool system has a connection plate which is to be arranged between acapacitor plate and one mould half of the tool, or on a side of acapacitor plate facing away from a mould half of the tool, and which hasthe media connections and/or media passages and/or media openings forthe supply and/or removal of media from or to the outside and to or fromthe one or more hollow spaces of the mould half, wherein the connectionplate preferably has pipe sections which, when the connection plate isfitted as specified, extend into the one or more hollow spaces of themould half.
 21. A method for production of one or more particle foamparts by welding of foam particles using electromagnetic waves, whereina tool with two mould halves forming a mould cavity is arranged betweentwo capacitor plates, the mould cavity is filled with foam particles,the tool is closed by bringing the two mould halves together, and thetool with the foam particles is subjected to electromagnetic waves, inparticular radio waves or microwaves, introduced into the mould cavityvia the capacitor plates, wherein the foam particles are heated by theelectromagnetic waves and at least partially fuse or bake together,wherein the method is implemented using a tool comprising two mouldhalves which bound a mould cavity, wherein at least one of the two mouldhalves is made of a material which is transparent to electromagneticwaves and has a boundary wall which bounds the mould cavity and one ormore supports serving to support the boundary wall on a capacitor plateon a side facing away from the mould cavity and forming one or morehollow spaces between the boundary wall and the capacitor plate, andwherein a relation of a volume of the one or more supports and airwithin the one or more hollow spaces of the two mould halves is adjustedsuch that a resulting relative permittivity of the tool is adapted to arelative permittivity of the foam particles, such that a temperature inthe foam particles is levelled as a whole or can be locally adjusted atneed.
 22. The method according to claim 21, wherein one or more trimmingbodies or a trimming fluid may be provided in the one or more hollowspaces, in order to influence an electromagnetic field in the mouldcavity.
 23. The method according to claim 21, wherein depending on thequality of the welding of the foam particles, the arrangement of one ormore trimming bodies or a trimming fluid in the tool is changed, inorder to adjust the influencing of the electromagnetic field in themould cavity.
 24. The method according to claim 21, wherein anarrangement of one or more trimming bodies or a trimming fluid in thetool is varied during a foaming process, in order to have dynamicinfluence on an electromagnetic field in the mould cavity.